Today we will have a detailed discussion on the NAMUR NE 43 standard. This NAMUR NE 43 standard is widely used for detailed troubleshooting of transmitters working on 4 mA to 20 mA signals.
What is NAMUR NE 43?
It is a standard that is widely used for troubleshooting a transmitter failure working on 4 mA to 20 mA signal type.
The NAMUR NE 43 has defined certain limits of analog values through which the system decides what is the problem in the transmitter.
Why is NAMUR NE 43 required?
In a conventional 4 mA to 20 mA signal, we can only know whether the transmitter is working ok or not.
If the mA goes below 4 mA or exceeds 20 mA, then a fault will be generated. Then the instrument person has to go into the field and check what the actual problem is.
But using NAMUR NE 43, we can directly come to know whether the transmitter is working in under range or over range or whether the transmitter is faulty or has any cabling issue.
How does NAMUR NE 43 identify under-range or range or the transmitter is faulty or any cabling issue?
In NAMUR NE 43, various mA levels indicate various problems. Various problems can be
- Transmitter in Under Range
- Transmitter in Over Range
- Transmitter Failure
- Cable Short Issue
- Cable Open Issue
But now the question is how is this possible through only a 4 mA to 20 mA signal? Let us have a look into how NAMUR NE 43 identifies under-range, over-range, transmitter failure, or any other cable issue like an open circuit or short circuit.
1. Transmitter in Under Range
Whenever the transmitter gives an output signal between 3.8 mA and 4 mA, the transmitter is sensing under range value.
2. Transmitter in Over Range
Whenever the transmitter gives an output signal between 20 mA and 20.5 mA, the transmitter is sensing under over value.
3. Transmitter Failure
Whenever the transmitter gives an output signal between 3.6 mA and 3.8 mA or between 20.5 mA and 22 mA, the transmitter fails.
4. Cable Short Issue
Whenever the transmitter gives an output signal between 0 mA and 3.6 mA, the cable is either fully cut or partially cut.
This method of identifying the open cable is also known as Live Zero and that is why we keep 4 mA as a transmitter lower range output value.
5. Cable Open Issue
Whenever the transmitter gives an output signal above 22 mA, the cable is in short condition and hence transmitting high current.
In the end, as an end user whether you have to use NAMUR standard in your transmitter or not, and what are the cost implications in a normal transmitter and with NAMUR NE 43 enabled transmitter?
The answer is if you see the cost difference between normal and NAMUR transmitters, you only have to pay 10-50$ more on NAMUR 43 compatible transmitters in Rosemount. If you want more information then you have to discuss it with the vendor.
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